Asteroid 2019 CM5 passed by the Earth at a distance of about 531 500 km (1.38 times the average distance between the Earth and the Moon, or 0.36% of the distance between the Earth and the Sun), slightly before 3.05 pm GMT on Friday 8 February 2019. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2019 CM5 has an estimated equivalent diameter of 5-16 m (i.e. it is estimated that a spherical object with the same volume would be 5-16 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 40 and 25 km above the ground, with only fragmentary material reaching the Earth's surface.
2019 CM5 was discovered on 11 February 2019 (three days after its closest approach to the Earth) by the University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount Lemmon in the Catalina Mountains north of Tucson. The designation 2019 CM5 implies that the asteroid was the 130th object (object M5 - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 24, so that M5 = (24 x 5) + 10 = 130) discovered in the first half of February 2019 (period 2019 C).
2019 CM5 has an 766 day orbital period and an eccentric orbit tilted at an angle of 0.40° to the plane of the Solar System, which takes it from 0.98 AU from the Sun (i.e. 98% of the the average distance at which the Earth orbits the Sun) to 2.29 AU from the Sun (i.e. 229% of the average distance at which the Earth orbits the Sun, and somewhat more than the distance at which Mars orbits). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that close encounters between the asteroid and Earth are extremely common, with the last having occurred in April 2017 and the next predicted in April 2126.
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